The correct sequence of these activities is________________?

Consider the following activities in a building construction?
1. Concreting of roof slabs
2. Brick-jelly lime concrete terracing
3. Erection of form work for slab
4. Construction of parapet wall in terrace
A. 1,3,2,4
B. 3,1,4,2
C. 3,1,2,4
D. 1,3,4, 2